These agreements (which are common) cover television, not Internet.
It's certainly the building's fault as well, but if Verizon really cared about expanding FiOS Internet, they'd agree to provide Internet service to a building even without providing television service[0].
Either way, whoever's fault it is, though, it's certainly not De Blasio's fault (which you asserted in your original post).
[0] Which they did do in the early days in some districts out in Long Island, but they stopped this around the same time as they stopped expanding FiOS into new areas.
It's certainly the building's fault as well, but if Verizon really cared about expanding FiOS Internet, they'd agree to provide Internet service to a building even without providing television service[0].
Either way, whoever's fault it is, though, it's certainly not De Blasio's fault (which you asserted in your original post).
[0] Which they did do in the early days in some districts out in Long Island, but they stopped this around the same time as they stopped expanding FiOS into new areas.